南大東島の隆起サンゴ礁段丘上の土壌(第2報) : 粘土鉱物組成について

概要

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Clay mineral composition was investigated on the soils formed on the raised coral limestone terraces under humid subtropical maritime climate of Minami-Daito Island. The outline of results is as follows: 1) On the higher terraces, Haguue (45〜50 m.a.s.l), Red soil (Haplic Lixisol, Typic Rhodudalf) and Yellow soil (Haplic Acrisol, Typic Kandiudult) mainly contained kaolinite, illite, gibbsite and goethite. The content of kaolinite in Yellow soil was higher than that of Red soil. 2) On the lower terraces, Hagushita (15 m.a.s.l.), clay mineral composition of Terra-rossa-like soil (Haplic Lixisol, Typic Hapludalf) was similar to those of Red soil and Yellow soil, except that a small amount of vermiculite was present in this soil. 3) On the sea side slope (20 m.a.s.l.), Terra fusca-like soil (Chromic Luvisol, Typic Hapludalf) mainly contained vermiculite, kaolinite and illite with a small amount of gibbsite and goethite. Judging from the fact that Red and Yellow soils of Minami-Daito Island mainly contained kaolinite and gibbsite, they are similar to the lateritic red soils in subtropical South China, and also considered to be older in the period of soil genesis and in more advanced development stage than the Red-Yellow soils (Udults) from Southwest Japan.
1997-06-30